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One of the best things for Kate Mara about starring in "Megan Leavey" was Varco the dog.

Varco is the Rex to Mara's Leavey in the true story of a young Marine corporal and her fight to bring her combat dog home after service in Iraq.

"He and I trained together, so by the time we started shooting we were very comfortable with each other," Mara told The Associated Press in a recent interview. "I loved working with a dog. They're unexpected and constantly doing things that you're not expecting them to do. If you want them to just sort of sit there during a scene they will, but then they'll do some genius little movement or sound or whatever that will make the scene that much better."

Mara, an animal activist who has worked with both Oceana and the Humane Society, also had the rare treat of being directed by a woman, Gabriela Cowperthwaite. She had also directed the orca-abuse film "Blackfish." In fact, Mara said, her animal advocacy blossomed due to the SeaWorld film.

"I've been acting since I was 14 and I would say in the past three years I've worked with more females than I ever have in my entire career, and that's directors but also actors," Mara said. "And we had so many females on our crew as well, so I definitely think that's changing. I think it's slower than we'd all like but it makes me so happy that something like 'Wonder Woman' is actually proving that fact. It'll make it easier and easier to make more and more films."

Mara's not interested in directing, but she has started her own production company.

"I love directors so much and I like it when they tell me what to do," she said.

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As for dogs, she has two of her own, both Boston terriers. At 14 and 15, she said, "They're doing really well."

Mara recently got engaged to "Billy Elliot" actor Jamie Bell, but she was tightlipped about her nuptials.

"I'm definitely not very girlie about it all. I'm just, like, I'll show up. My fiance is much more specific and much more opinionated than I am so it's nice. I just sort of let him do it."

One of the wedding challenges: She's vegan and Bell's not, "so you've got to make everybody happy."

The film, which opened Friday, covers raw territory for veterans coping at home with post-combat trauma. Mara wanted to get it right, leaning on her previous role as the wife of a vet in the 2015 release "Man Down."

"That movie is what really made me want to find some sort of a female Marine story," she said. "We want Marines and families of soldiers to be able to watch the film and not just think 'oh yeah, the war stuff looks real but how about when you go home?' We wanted that to feel as authentic."